Maintaining good water and soil quality in catchments containing deer farms

Abstract

A three year study was undertaken to determine the effect of farmed deer on soil and water quality in two catchments in southern New Zealand. The objective was to benchmark their effects and try to incorporate some of the best management practices tested during the 3 yrs of study designed to mitigate any deleterious effects. Most sampling sites seldom met national guidelines for good surface water quality in lowland streams (eutrophication for nitrite/nitrate‐N = 0.444 mg N L⁻¹, dissolved reactive phosphorus = 0.01 mgP L⁻¹ and total phosphorus = 0.03 mg P L⁻¹; fish toxicity for ammoniacal‐N = 0.9mgNL⁻¹; and contact recreation for Escherichia coli = 260cfu 100mL⁻¹). However, a sedimentation pond in one catchment and a riparian area fenced‐off and set aside in‐perpetuity caused decreases in loads of contaminants exiting catchments. Data gathered during the study showed that the planting of trees and provision of shelter could help mitigate some containment transfer associated with fence‐line pacing, while fencing‐off and planting wallowing areas significantly decreased contaminant loads in streams. However, an alternative wallowing site should be provided to accommodate deer behaviour otherwise deer will make a new wallow a short distance away from the old one that will also likely be connected to a waterway. An environmental‐economic analysis for P losses indicated that decreasing soil Olsen P concentrations to the minimal agronomically possible was cost beneficial, but only decreased P losses by 0.2 kgPha⁻¹yr⁻¹. Larger decreases (∼ 1 kgPha⁻¹ yr⁻¹) were estimated to occur if wallows were fenced‐off, planted and alternative wallowing sites installed. As a result of these data, some of the best management practices (BMPs) have been undertaken within the catchments and will improve soil and water quality in the future. However, farmers should be presented with a range of BMPs tested on an environmental and economic basis in order to fully assess their suitability to a farm.

Keywords:

• Best management practice
• fencing‐off
• riparian
• sedimentation
• sustainability
• water quality